You can start by looking on fanfiction.net. It has a large collection of fan - created stories, and there's a good chance you'll find some Highlander SG1 crossovers there.
One interesting story could be about how the characters from Highlander and SG1 team up to fight a common enemy that has the ability to travel between different dimensions. This would bring together the immortality concept from Highlander and the inter - galactic exploration of SG1.
A possible plot could involve an immortal villain from the Highlander world using the Stargate network to spread chaos across different planets. The SG1 team, with the help of some friendly Highlander characters, has to track him down and stop him before he causes too much destruction.
Sam Carter and Methos would be a fascinating combination. Sam's scientific genius could be intrigued by Methos' ancient knowledge and long - lived existence. Methos might also be able to offer some unique perspectives on the technology Sam deals with in the Stargate program, and together they could come up with innovative solutions to problems.
One great sg1 crossover fanfiction could be the ones that cross it with 'Star Trek'. In such stories, characters from SG1 might find themselves in the Star Trek universe facing new challenges and meeting different alien species. It's really interesting to see how the different technologies and cultures interact.
The different character dynamics are also unique. You have Buffy, a strong - willed slayer, interacting with Colonel O'Neill and his team. Their different ways of handling problems, like Buffy's more instinctive approach compared to the military strategy of SG1, make for great story - telling.
I like 'Buffy in the SGC'. In this fanfic, Buffy is somehow transported to the Stargate Command. The author does a good job of showing how Buffy's slayer skills are both useful and a bit out of place in the military - science - fiction setting of Stargate. There are some really cool fight scenes against Goa'uld with Buffy leading the charge.
One common theme is the clash of different cultures. In SG - 1, there are various alien cultures, and in NCIS, there's the military and law - enforcement culture. When they cross over, seeing how these cultures interact is a big part of the story. For example, how the NCIS agents react to the advanced technology and strange alien customs from SG - 1.
The uniqueness lies in the combination of two very different universes. NCIS is a modern - day crime - solving show, while Highlander has elements of immortality and a different kind of combat. When crossed over, it can create stories that are full of contrasts and new possibilities.
You can try fanfiction websites like Archive of Our Own (AO3). It has a large collection of various fanfictions, including Highlander crossovers. Just use the search function and type in 'Highlander Crossover' to find relevant stories.
Yes, there are likely some interesting ones out there. A good place to start looking could be on fanfiction websites like Archive of Our Own. Some might explore how the characters from NCIS interact with those from Highlander in unique crime - solving scenarios or character - development arcs.